Method and apparatus for continuous cutting and joining of thermoplastic sheet material

ABSTRACT

A method and means for continuously cutting and sealing thin gauge thermoplastic sheet material using kinetic energy produced by a horn of reduced sealing area.

United States Patent Sager 11s] 3,657,d33 [451 Apr. 18, 11972 METHOD ANDAPPARATUS FOR CONTINUOUS CUTTING AND JOINING OF THERMOPLASTIC SHEETMATERIAL Inventor: Thomas B. Sager, Plymouth Valley, Pa.

Ultrasonic Systems, Inc., Farmingdale, NY.

Filed: Mar. 26, 1969 Appl. No.: 810,638

Assignee:

U.S. Cl ..156/73, 156/580, 156/251,

156/515 Int. Cl. ..B29c 27/08 Field ofSearch ..l56/73,251,5l5,580

References Cited UNITED STATES PATENTS 3,378,429 4/1968 Obeda ..156/5153,401,446 9/1968 Obeda et a1 156/584 3,457,132 7/1969 Tuma et a1..156/515 Primary Examiner-Samuel Feinberg Attorney-Sherman Levy [5 7]ABSTRACT A method and mea'ns for continuously cutting and sealing thingauge thermoplastic sheet material using kinetic energy produced by ahorn of reduced sealing area.

5 Claims, 7 Drawing Figures PATENTED APR 18 I972 INVENTOR THoMAs B.SAGE!!- BY 4g? ATTORNEY METHOD AND APPARATUS son CONTINUOUS CUTTING ANDJOINING OF THERMOPLASTIC SHEET I MATERIAL The present invention relatesto a horn to be used as part of a machine that will seal and cut thinthermoplasticon a continuous operating basis at speeds such as thosethat are suitable for packaging applications.

An object of the present invention is to provide an improved method andmeans for sealing and cutting thin thermoplastic or a continuousoperating basis at suitable speeds, and wherein the special horn hasmany uses in manufacturing of products such as in sealing heatshrinkable materials of a thermoplastic type and creating a bond on acontinuous basis that is either linear or non-linear without shrinkingthe film, and wherein the present invention also permits the born toremain clean and free of plastic melt.

Another object is to provide a horn which has a new and original sealand cut tool, as well as a tool that is useful in packaging, and inaddition there is provided a tool that is practical and because of itssealing rate it can be easily and readily applied to various types ofpackaging machines or equipment, the horn remaining clean and free ofcontamination at all times when sealing and cutting.

In addition, the resent invention does not allow noticeable shrinkagewhen bonding and cutting heat shrinkable films, and the device is easyto install on existing packaging machinery or equipment in areas wherecontinuous sealing occurs or is needed.

Further objects and advantages are to provide improved elements andarrangements thereof in a device of the character described that iseconomical to produce, durable in form, and conducive to the mosteconomical use of materials and unifonnity of members formed therefrom.

Still further objects and advantages will become apparent from thesubsequent description in thespecification.

IN THE DRAWINGS:

FIG. 1 is a fragmentary perspective view of an ultrasonic horn and anvilillustrating the process of the present invention for cutting andsealing plastic.

FIG. 2 is a side elevational view of the device shown in FIG. 1;

FIG. 3 is a fragmentary perspective view of a plastic tube or memberthat has been cut and sealed in accordance with the present invention;

FIGS. 4A, 4B, 4C and 4D are fragmentary elevational views illustratingvariations or modifications in the horn or blade configuration.

Referring in detail to the drawings, the numeral indicates a horn thatis part of a kinetic machine, and the horn is adapted to be used forsealing and cutting thin thermoplastic such as the thermoplastic 11 on acontinuous operating basis. The arrow indicated by the numeral 12 inFIG. 1 indicates the direction of movement of the film.

As shown in the drawings, there is provided an anvil which is indicatedby the numeral 13, and anvil 13 may have an inclined surface 14 for apurpose to be later described. The

thermoplastic 11 may consist of folded sheets or sections 15 which arefolded about the fold line 16. The numeral 17 indicates a seal and cutblade, and the numerals 18 and 19 indicate the combination impact andshear action respectively. The numeral 20 indicates a waste strip thatis formed when using the present invention. TI-Ie numeral 21 indicatesthe area where the cut is made so that the waste strip 20 separates fromthe remaining portion of the thermoplastic. The adjacent edge of theplastic 11 is bonded or sealed by a molecular bond as at 22, and inaddition, the waste strip will also have a corresponding molecular bondalong the edge where it is severed from the remaining portion of theplastic.

In FIG. 3, the numeral 23 indicates a completed product or tube that ismade when using the process and means of the present invention.

Referring now to FIGS. 4A, 4B, 4C and 4D, the numerals 24, 25, 26 and 27indicate various different shapes or configurations or the bladesshowing various radii that can be used.

It will therefore be seen that in accordance with the present inventionthere has been provided a method of and means for sealing and cuttingthin thermoplastic on a continuous operating basis and when using thepresent invention, thermoplastic film such as the film 11 may be foldedover upon itself to form the two sections or sheets 15 and this plasticmay be folded over upon itself along the crease line or fold line 16.The plastic 11 is adapted to be advanced by any suitable mechanism inthe direction indicated by the arrow 12 in FIG. 1 so that for examplethe plastic 11 may move from left to right in FIG. 1.

With the horn l0 suitably actuated by or energized by transducer of anultrasonic machine, it will be seen that with the blade 17 connected tothe horn 10 the blade 17 will exert or provide a combination impact andshear action as indicated by the arrows l8 and 19 in FIG. 1. This willresult in or cause a cut to be made along the line 21, and at the sametime the plastic will be sealed along the edge or line 22 so that afinished product or tube 23 will be provided as shown in FIG. 3

Instead of using the blade 17, as shown in FIGS. 1 and 2, blades ofdifferent radii or configuration may be used, and for example, FIGS. 4A,4B, 4C and 4D indicate blades 24, 25, 26 and 27 which may be used ifdesired or required.

It is to be understood that the parts can be made in different shapes orsizes as needed or desired, and any suitable materials can be used formaking the various elements or parts.

With further reference to the present invention using the kinetic energyborn to seal and cut thin plastic on a continuous operating basis,ultrasonic frequency in the range of about 20 kcs can be used to developthe seal, and it is to be understood that such kinetic energy includesmechanical vibrations at various frequency ranges of sonic andultrasonic.

It will therefore be seen that there has been provided a horn which maybe part of a predeveloped K.E. machine that will seal and cut thinthermoplastic on a continuous operating basis at speeds suitable bypackaging companies and the like. The seal and cut horn is highlyadvantageous over previous or standard I(.E. bonding horns andtechniques for sealing thermo-sheet plastics, and for example, it hasbeen found that the standard methods and sealing horns will not achievea satisfactory seal in very thin thermoplastic films.

Thus, K.E. induced in the thin films will either pass through theplastic sheets and into the back-up anvil which acts as an energy sinknot allowing required temperatures to achieve a molecular thermo bond.In addition, it is believed that the material, being thin in gauge, wasnot resilient enough to generate temperatures required for a molecularthermo bond, and the I(.E. heat losses were carried off by the back-upanvil. In order to overcome these disadvantages, there has been providedthe special horn for sealing that will generate enough K.E. losses inthe thinfilms to effect or bring about a good molecular thermo bond.

In addition, by reducing the sealing area of the horn, and with theconstruction that permits the thermo film to pass under and in adirection that allows continuous even liquid fiow of plastic that isbeing produced by the special horn, the sheets will fuse together in alinear or non-linear direction. In addition, in order to achieve thisbond, it requires cutting the film, that is thinning the area of plasticunder the sealing born to cause complete severing and this allowsmaximum plastic flow to either side of the sealing horn to act as afiller to create a strong thermo molecular bond.

The horn of the present invention has many uses in manufacturing variousproducts. For example, it is especially suitable or useful in sealingheat shrinkable materials of the thermoplastic type and creating acontinuous bond, either linear or non-linear without shrinking thefilrn, and also allows the horn to remain clean and free of plasticmelt. Further, it provides that breakaway seals can be accomplished forpackages requiring this type of seal, and control of breakaway strengthcan be accomplished by the type of thermoplastic sheet and the gauge ofthe thermoplastic sheet, and in addition the control of breakawaystrength can be controlled by the amount of K.E. induced at a moment oftime and this is related to the sealing rate and power (K.E.) available,or a combination of both.

Attention is directed to the fact that various mechanical systems can beused with this horn for the sealing and cutting operations, and theparticular or specific machine is not of special concern for thepurposes of this patent application, although the configuration of thehorn is, and the function of the horn is of major importance.

Thus, it will be seen that there has been provided a horn that willsolve many packaging problems that occur in the bonding of thinthermoplastic sheets into tubes and other geometric figures withoutcausing such problems as the shrinkage of films, uncontrolled breakawayseals for flexible and non-flexible packages, and the like.

There has thus been provided a new and original seal and cut tool, atool useful in packaging, and a tool that is practical because of itssealing rate, ease of application to packaging equipment, and inaddition, due to the fact that the horn remains clean and free ofcontamination at all times when sealing and cutting. Further, it doesnot allow noticeable shrinkage when bonding and cutting heat shrinkablefilms. Also, the device is easy to install on most existing packagingequipment or machinery in areas where continuous sealing occurs or isutilized.

FIG. 3 illustrates an end product such as a tube as indicated by thenumeral 23, which may have a hermetic seal. Various types of sheetplastics may be used, such as polypropylene, vinyls, and the like.

The sealing tip of the horn may vary in radius to assure proper flow ofmelted plastic which will produce the desirable bond strength needed forthat particular product.

The seal and cut horn remains clean and free of plastic melt during thesealing operation because the sealing tip on the horn remains at roomtemperature, which is far lower than the melting point of thethermoplastic film being sealed and cut. This permits incompatibility toadhesive bonding between the sealing tip and the film.

The inclined plane designed in the anvil allows the sealing tip of thehorn to produce forces in shear and impact. These two forces, whencombined, will cut and seal thermoplastic films. A higher percentage ofshear force will reduce material wear between the horn tip and the anvilin contact during sealing. Direct impact can cause the horn tip or anvilto deform and render it unusable for sealing.

In addition, the energy developed through this mass in motion, being theultrasonic horn, prevents shrinkage in the sealed area. This is due tothe fact that the horn is below the melting temperature of the plasticit contacts. Also, the area being sealed can be considered a locus ofsmall melted points, these points being imparted at a rate ofapproximately 20,000 cycles per second. Thus, continuous welding occurs.There is no energy, in the form of heat, radiated other than the pointwhich is directly contacted by the horn.

Although the invention has been herein shown and described in what isconceived to be the most practical and preferred embodiment, it isrecognized that departures may be made therefrom within the scope of theinvention, which is not to be limited to the details disclosed hereinbut is to be accorded the full scope of the claims so as to embrace anyand all equivalent devices and apparatus.

I claim:

1. A method of ultrasonically simultaneously sealing and cutting thinthermoplastic sheets on a continuous operating basis with the aid of ablade having a radius contacting edge, comprising the steps of:

A. providing an anvil having an inclined surface,

B. overlapping said sheets in contact with each other on said inclinedsurface, C. positioning said blade such that said radius contacting edgeapplies a small compressive force to said sheets along a line traversingthe area of overlap,

D. moving said plastic sheets and said anvil and said blade relative toeach other,

E. vibrating the contacting edge of said blade at an ultrasonic rate toapply recurring force to said sheets with said recurring force having acombination of impact action by a substantial component perpendicular tosaid contacting edge and shear action having a substantial componentparallel to said inclined surface of said anvil to generate sufficientkinetic energy at the area of contact with said blade to simultaneouslycut and seal said sheets as they are moved relative to said blade.

2. The method as defined in claim 1, wherein in said moving step saidplastic sheets are moved along said inclined surface relative to saidblade.

3. The method as defined in claim 1, wherein in said moving step saidanvil and said blade are moved relative to said plastic sheets.

4. Apparatus for ultrasonically simultaneously sealing and cutting thinthermoplastic sheets on a continuous operating basis comprising A. ablade having a radius contacting edge,

B. an anvil having an inclined surface in spaced relation to said bladefor a spacing therebetween to receive the everlapping sheets in contactwith each other on said inclined surface and said radius contacting edgeapplying a small compressive force to said sheets along a linetraversing the area of overlap as said plastic sheets move along saidinclined surface relative to said blade, and

C. means for vibrating the contacting edge of said blade at anultrasonic rate to apply an additional recurring force to said sheetswith said recurring force having a combination of impact action by asubstantial component perpendicular to said contacting edge and shearaction having a substantial component parallel to said inclined surfaceof said anvil to generate sufficient kinetic energy at the area ofcontact with said blade to simultaneously cut and seal said sheets asthey are moved relative to said blade.

5. Apparatus as defined in claim 4, wherein said blade has a curvilineartapered edge adapted to allow for the proper flow of melted plasticwhich produces the bonding strength necessary to form said seal.

1. A method of ultrasonically simultaneously sealing and cutting thinthermoplastic sheets on a continuous operating basis with the aid of ablade having a radius contacting edge, comprising the steps of: A.providing an anvil having an inclined surface, B. overlapping saidsheets in contact with each other on said inclined surface, C.positioning said blade such that said radius contacting edge applies asmall compressive force to said sheets along a line traversing the areaof overlap, D. moving said plastic sheets and said anvil and said bladerelative to each other, E. vibrating the contacting edge of said bladeat an ultrasonic rate to apply recurring force to said sheets with saidrecurring force having a combination of impact action by a substantialcomponent perpendicular to said contacting edge and shear action havinga substantial component parallel to said inclined surface of said anvilto generate sufficient kinetic energy at the area of contact with saidblade to simultaneously cut and seal said sheets as they are movedrelative to said blade.
 2. The method as defined in claim 1, wherein insaid moving step said plastic sheets are moved along said inclinedsurface relative to said blade.
 3. The method as defined in claim 1,wherein in said moving step said anvil and said blade are moved relativeto said plastic sheets.
 4. Apparatus for ultrasonically simultaneouslysealing and cutting thin thermoplastic sheets on a continuous operatingbasis comprising A. a blade having a radius contacting edge, B. an anvilhaving an inclined surface in spaced relation to said blade for aspacing therebetween to receive the everlapping sheets in contact witheach other on said inclined surface and said radius contacting edgeapplying a small compressive force to said sheets along a linetraversing the area of overlap as said plastic sheets move along saidinclined surface relative to said blade, and C. means for vibrating thecontacting edge of said blade at an ultrasonic rate to apply anadditional recurring force to said sheets with said recurring forcehaving a combination of impact action by a substantial componentperpendicular to said contacting edge and shear action having asubstantial component parallel to said inclined surface of said anvil togenerate sufficient kinetic energy at the area of contact with saidblade to simultaneously cut and seal said sheets as they are movedrelative to said blade.
 5. Apparatus as defined in claim 4, wherein saidblade has a curvilinear tapered edge adapted to allow for the properflow of melted plastic which produces the bonding strength necessary toform said seal.